This right here is the reason the Emperor is pissed off. To her mind, it sounds like Yingying has many other women on the side so she doesn't have to pine on someone unattainable.
There are reasons, though not good reasons from my perspective. Monthly series like this are typically split into 2 or 3 parts on digital platforms to reduce the waiting time between releases, and also to charge you more for reading them.
If he was with one of them then he wouldn't come the reunion alone. Though there is still the possibility that he dated and broke up during the timeskip.
The description wasn't there when you commented. I was hesitant to mention the connection with Tsurezure Biyori, because it could deter people who are not familiar with that series. In the end, I figured adding a note that this story can be enjoyed without any knowledge of Tsurezure Biyori was...